The present invention relates to internal combustion engine turbochargers, and, more particularly, to a radial turbocharger having variable nozzle geometry.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine.
An internal combustion engine may include one or more turbochargers for compressing a fluid to be supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases from the engine, and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chambers. The fluid compressed by the compressor may be in the form of combustion air only, or may be a mixture of fuel and combustion air. Through the use of a turbocharger, the power available from an engine of given size can be increased significantly. Thus, a smaller, less expensive engine may be used for a given power requirement, and power loss due to, for example, changes in altitude, can be compensated for.
Sizing a turbocharger for proper performance under all engine operating conditions can be difficult. In an exhaust gas turbocharger, exhaust gas flow and turbine design determine turbine performance, and thereby compressor performance and turbocharger efficiency. Vanes in the inlet throat or outlet nozzle of the turbine can be used to influence flow characteristics through the turbine, and thereby the turbine power generated for a given exhaust gas flow. If the engine is to be operated at or near full load during most of its operating cycle, it is not difficult to design the turbocharger for efficient performance. However, if the engine is to be operated at significantly less than full load for extended periods of time, it becomes more difficult to design a turbocharger that will perform well throughout the operating range of the engine. Desirably, the turbocharger will provide the required level of pressure boost, respond quickly to load changes, and function efficiently under both high load and low load conditions.
For an engine having a wide range of operating load, it has been know to size the turbine for proper performance under full load conditions. A problem with this approach is that the turbocharger responds slowly at low speed, and the boost pressure available at low engine speeds is minimal. As an alternative, it has been known to provide a turbine design that exceeds the power requirements at full load, and to use a waste gate to bypass excess exhaust gas flow after the turbocharger has reached the desired boost level. An xe2x80x9coversizedxe2x80x9d turbine of this type will provide greater boost at lower load conditions, and will respond more quickly at lower speeds, but engine back pressure is increased and the energy in the bypassed exhaust flow is wasted.
It is known to control turbocharger performance by controlling exhaust gas flow through the turbine of the turbocharger. Controllable vanes in the turbine throat and/or nozzle exit have been used to control turbine efficiency, and thereby turbocharger performance. Pivotable vanes connected by linkage to a control ring have been used. Rotation of the ring changes the vane angle, and thereby the flow characteristics of the exhaust gas through the turbine. U.S. Pat. No. 4,490,622 discloses a turbocharger in which nozzle vanes are spaced circumferentially about the turbine rotor, and a control linkage controls the position of the nozzle vanes, to vary the flow of exhaust gases to the turbine.
Many of the known variable nozzle designs are complex, having numerous pivotal connections and complex linkages. Such complex designs may be prone to failure and wear.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, an internal combustion engine is provided with a plurality of combustion cylinders; an exhaust manifold coupled with the combustion cylinders; and an intake manifold coupled with the combustion cylinders. A turbocharger includes a turbine defining an exhaust gas flow path having a turbine inlet coupled with the exhaust manifold and a turbine outlet, and a compressor having a compressor inlet and a compressor outlet. The compressor outlet is coupled with the intake manifold. An adjustable vane assembly is provided for at least one of the turbine inlet and the turbine outlet. The adjustable vane assembly includes a housing, and a controllable vane cartridge disposed in the housing. The cartridge has vanes therein, the vanes having a plurality of vane sections each configured in a different vane geometry. An adjustment device is associated with the cartridge, the cartridge having different positions in the housing placing different vane sections in the exhaust gas flow path.
In another aspect of the invention, turbocharger is provided with a turbine defining an exhaust gas flow path therethrough, a turbine inlet to the flow path and a turbine outlet from the flow path. A compressor is driven by the turbine and includes a compressor inlet and a compressor outlet. An adjustable vane assembly for at least one of the turbine inlet and the turbine outlet includes a housing, and a controllable vane cartridge disposed in the housing. The cartridge has vanes therein, the vanes having a plurality of vane sections each configured in a different vane geometry. An adjustment device associated with the cartridge has different positions in the housing placing different vane sections in the exhaust gas flow path.
In yet another aspect of the invention, a method of operating an internal combustion engine, is provided with steps of providing a plurality of combustion cylinders, an first exhaust manifold and an intake manifold; transporting exhaust gas from the combustion cylinders to the exhaust manifold; providing a turbocharger including a turbine having an exhaust gas flow path there through, a turbine inlet and a turbine outlet, and a compressor having a compressor inlet and a compressor outlet; providing an adjustable vane assembly for at least one of the turbine inlet and the turbine outlet, and providing in the vane assembly a housing, and vanes having a plurality of vane sections each of a different vane geometry, and an adjustment device for moving the vane sections into and out of the flow path; rotatably driving the turbine with exhaust gas introduced at the turbine inlet; introducing combustion gas at the compressor inlet; transporting combustion gas from the compressor outlet to the intake manifold; sensing at least one of operating conditions of the engine and performance of the turbocharger; controlling the adjustment device in response to at least one of the engine operating conditions and the performance of the turbocharger; moving the vanes in the housing; and positioning a selected vane section in the exhaust gas flow path.